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Submeters Measure Energy Savings, Help Drive Campus-Wide Building System Upgrades


Ravenscroft School wanted an economical way to monitor and evaluate energy and natural gas use on campus. Submeters were chosen for their ability to tie into the building management system to centrally monitor the school’s energy profile. In the process, facility managers learned more about how, when and where the energy was being used—justifying new building system upgrades.

Founded in 1862, Ravenscroft School serves some 1,235 students in lower (pre-K-5), middle (6-8), and upper school (9-12) divisions on a 125-acre wooded campus in Raleigh, N.C. As a non-profit coeducational college preparatory day school with more than 200 full-time employees, Ravenscroft appears to be well on its way to becoming the area’s leading independent academic institution and one of the top schools of its kind in the Southeast. 

Ravenscroft Goes Green

Under the leadership of Doreen C. Kelly, Ravenscroft’s Head of School, weaving sustainability into the fabric of the school’s culture is playing out in a number of ways, including composting in the dining hall, reducing the school’s carbon footprint through more aggressive recycling, dual-flush toilets, light/motion sensors, and other energy conservation measures.

As the primary energy data acquisition tool, electric submeters provide accurate energy consumption and demand profiles for all metered buildings on a 24/7 basis. With the exception of the Murphy Hall chiller plant, in which only an electric meter was installed, other campus locations totaling more than 259,000 square feet were metered to track both gas and electricity.

Metering system supplies the data

Several months earlier, the school’s Sustainability Committee and the Board of Trustees initiated a comprehensive energy audit to benchmark Ravenscroft’s gas and energy use in seven major buildings on campus. As it turned out, the local utility’s data recording meters lacked the ability to integrate with the school’s building management system (BMS) to centrally monitor the school’s energy load. For that reason, the utility meters were also incapable of serving as a teaching tool to educated students and faculty on Ravenscroft’s on-going energy conservation initiatives.

One of 10 submeters monitoring 400 to 3200A circuits in seven campus buildings. The meter’s Modbus IP communications option allows direct connection to the building management system (BMS) via the Ethernet link plugged into the jack above the meter.

During the installation phase, the electrical contractor, Classic Electric Service, Inc., teamed with a local stocking distributor, Eck Supply, and E-Mon’s factory rep, Emery Electrical Sales, to complete the install and startup over a period of about three months. In operation since May 2010, energy data collection is provided by 10 submeters with Modbus IP communications (see Photo at left). The circuits being monitored include 277/480 volt, 3-phase service ranging from 400A to 3200A.

Building management system

Paralleling the metering system, the school’s BMS supports open protocols like LonWorks, BACnet, and Modbus to integrate lighting controls, electrical switchgear, generators, and other building systems into a total facility management system. An Internet-enabled meter dashboard and energy monitor provides real-time and historical displays of kWh, kW and other measurements from any access point in the system (see Photo below). The meter data is collected both wirelessly and hard-wired and is stored on the school’s network.

Results and a Look Forward

Chris Farrow, Director of Buildings and Grounds, reviews meter dash-board data used to baseline seasonal energy usage. The kWh / kW data helps the facilities staff optimize building system performance to reduce energy use and cut cost without impacting the comfort and quality of the classroom environment. The data also helps justify and prioritize building system upgrades and retrofits.

“Our enhanced understanding of usage patterns and variations has helped drive decisions to perform a lighting retrofit and measure the results,” says Leonard Johnson, Assistant Head of School for Business and Finance. “In addition, the meters have provided the rationale for investing in upgraded building management systems across some of our larger buildings.”

As a learning tool, teachers now use the meter dashboards to demonstrate how energy consumption is being monitored. By comparing historical and current levels, students can contrast the facility’s original energy consumption before the meters were installed with its current savings in terms of energy units, dollars and reduced carbon emissions. One teacher even tags certain energy-consuming items in his building and manually shuts them down so the students can monitor real-time reductions in energy use and carbon emissions.

“Beyond that,” notes Johnson, “the data also helps us to establish seasonal energy usage baselines, prioritize upgrades and retrofits and adjust occupied-versus-unoccupied operating hours to reduce energy use and save money without sacrificing the comfort and quality of the classroom environment.”

Project Partners

Mechanical Contractor: Newcomb and Company, Raleigh, N.C.:

E-Mon Factory Rep: Emery Electrical Sales, Inc., Charlotte, N.C.:

Electrical Distributor: Eck Supply, Raleigh, N.C.:

Electrical Contractor: Classic Electric Service, Inc., Raleigh, N.C.: 919-834-3226

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